With continuous development of Internet technologies, the Internet Protocol is also continuously updating. With the update of the Internet Protocol, a networking method is also continuously updating. In networking of the Internet Protocol Version 6 (IPv6), a networking method of connecting a broadband access server (BAS) to a router and connecting the router to a terminal is often used.
In an existing IPv6 network, the BAS may configure a server local prefix and a server delegate prefix for an interface service of the router connected to the BAS. The BAS may configure, according to the server local prefix, an Internet Protocol (IP) address for a wide area network (WAN) interface that is on the router and that is connected to the BAS. The BAS may send the server local prefix and the server delegate prefix to the router. The router may generate a local prefix of the router according to the server delegate prefix and obtain an IP address of a local area network (LAN) interface of the router according to the local prefix of the router, that is, an IP address of the terminal connected to the router. The router also obtains an IP address of the WAN interface of the router according to the server local prefix.
For an enterprise user or a large laboratory, generally there is only one ingress router connected to the Internet by using the BAS. Access of multiple terminals of different local area networks can be implemented by connecting routers to the ingress router to form a cascaded network. For a prefix obtaining method in the IPv6 network, the ingress router may obtain only one server delegate prefix from the BAS, that is, the ingress router has only one router local prefix. Therefore, in a cascaded network, a device connected to a cascaded router cannot obtain an IP address.